1. Field of the Invention
The present invention relates to a thermal treatment apparatus, a semiconductor device fabrication apparatus, a load-lock chamber of such a semiconductor device fabrication apparatus, and a method of fabricating a semiconductor device using such a thermal treatment apparatus or such a semiconductor device fabrication apparatus.
2. Description of the Prior Art
Recently, it has been of an important task in semiconductor fabrication technology to suppress the formation of a native oxide film. If a native oxide film is formed on a semiconductor substrate, then the leak current of a semiconductor device that is fabricated is increased, the dielectric strength thereof is lowered, and the operating speed thereof is adversely affected.
Various efforts have been made to suppress the formation of a native oxide film. For example, there has been developed a load-lock semiconductor device fabrication apparatus for suppressing the formation of a native oxide film which would otherwise be deposited on the surface of a semiconductor substrate by oxygen trapped in a reaction chamber in a vertical low-pressure chemical vapor deposition (LPCVD) system. The load-lock semiconductor device fabrication apparatus has a load-lock chamber disposed between the reaction chamber and the exterior space for holding the inlet of the reaction chamber out of contact with the atmosphere. After the load-lock chamber is evacuated, an N2 atmosphere is introduced into the load-lock chamber. Quantitative data have been acquired which indicate the relationship between the densities of oxygen in the load-lock chamber and the reaction chamber and the thickness of a native oxide film. The effectiveness of the load-lock chamber is being widely recognized in the art.
In CVD systems, it is known that a trace amount of oxygen leaks from the exterior into a semiconductor device fabrication apparatus, e.g., from the exterior through an O-ring of a reaction chamber of quartz into the reaction chamber. The oxygen leakage causes a native oxide film to be formed on a semiconductor substrate, and also degrades the characteristics of a thin film deposited on the semiconductor substrate. Examples of degraded characteristics include many grain boundaries in a crystalline thin film and wrong crystalline directions.
It is important that semiconductor device fabrication apparatus with load-lock chambers for mass-producing semiconductor devices fabricate semiconductor devices of stable and reproducible characteristics. However, there have not been proposed any significant means and systems for ensuring oxygen densities in load-load and reaction chambers for stable and reproducible semiconductor device characteristics. Furthermore, no measures are presently taken to prevent a trace amount of oxygen from leaking into semiconductor device fabrication apparatus.
It is known to monitor a moisture in sputtering apparatus. Japanese laid-open patent publication No. 3-152924, for example, discloses a monitoring process for photo-excited vapor phase processing. However, it has not been known to monitor the density of oxygen in semiconductor device fabrication apparatus or the like.
It is therefore an object of the present invention to provide a thermal treatment device capable of eliminating adverse effects which would otherwise be caused by residual oxygen.
Another object of the present invention is to provide a semiconductor device fabrication apparatus and a load-lock chamber which prevent a native oxide film from being formed on a semiconductor substrate thereby to fabricate a semiconductor device whose characteristics are not degraded by oxygen.
Still another object of the present invention is to provide a method of fabricating a semiconductor device using such a thermal treatment device or such a semiconductor device fabrication apparatus.
According to an aspect of the present invention, there is provided an apparatus for thermally treating a semiconductor substrate, comprising a thermal treatment device for thermally processing a semiconductor substrate, and an oxygen monitor for monitoring the density of oxygen in the thermal treatment device.
According to another aspect of the present invention, there is provided a load-lock assembly for holding a semiconductor substrate before thermal treatment thereof, comprising a load-lock chamber for housing a semiconductor substrate therein, and an oxygen monitor for monitoring the density of oxygen in the load-lock chamber.
According to still another aspect of the present invention, there is provided an apparatus for fabricating a semiconductor device, comprising a thermal treatment device for thermally processing a semiconductor substrate, a first oxygen monitor for monitoring the density of oxygen in the thermal treatment device, a load-lock chamber separably coupled to the thermal treatment device for housing the semiconductor substrate before thermal treatment thereof by the thermal treatment device, and a second oxygen monitor for monitoring the density of oxygen in the load-lock chamber.
The thermal treatment device may comprise a chemical vapor deposition device.
Each of the oxygen monitors may comprise a mass spectrum analyzer.
According to yet another aspect of the present invention, there is provided a method of depositing a thin film on a semiconductor substrate with a semiconductor device fabrication apparatus having a thermal treatment device associated with an oxygen monitor, the method comprising the steps of evacuating the thermal treatment device, thereafter, measuring the density of oxygen in the thermal treatment device with the oxygen monitor, introducing a semiconductor substrate into the thermal treatment device after the density of oxygen in the thermal treatment device as measured by the oxygen monitor has dropped below a predetermined level, and depositing a thin film on the semiconductor substrate in the thermal treatment device.
According to yet still another aspect of the present invention, there is provided a method of depositing a thin film on a semiconductor substrate with a semiconductor device fabrication apparatus having a thermal treatment device associated with a first oxygen monitor, and a load-lock chamber associated with a second oxygen monitor, the load-lock chamber separably communicating with the thermal treatment device, the method comprising the steps of introducing a semiconductor substrate into the load-lock chamber, then, evacuating the load-lock chamber, thereafter, measuring the density of oxygen in the load-lock chamber with the second oxygen monitor, evacuating the thermal treatment device, thereafter, measuring the density of oxygen in the thermal treatment device with the first oxygen monitor, introducing the semiconductor substrate from the load-lock chamber into the thermal treatment device after the densities of oxygen in the load-lock chamber and the thermal treatment device as measured by the first and second oxygen monitors, respectively, have dropped below a predetermined level, and depositing a thin film on the semiconductor substrate in the thermal treatment device.
Since the thermal treatment device and/or the load-lock chamber is associated with the oxygen monitor, the oxygen density in the thermal treatment device and/or the load-lock chamber can be monitored accurately at all times. If the monitored oxygen density in the thermal treatment device and/or the load-lock chamber is higher than the predetermined level, then the process of fabricating semiconductor devices can immediately be interrupted.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.